Optical Window Assembly with Backup Ring for Downhole Sensor Sealing
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Solution Overview
Problem
Existing downhole tools face challenges in effectively measuring and analyzing downhole fluids due to fluid leakage and pressure issues, which hinder accurate formation evaluation and fluid parameter measurement.
Innovation Solution
The optical window assembly, comprising a tubular sensor body with a metalized sapphire optical window, a seal, and a backup ring made of polyether ether ketone, is designed to prevent fluid leakage while allowing light to pass through, using a tapered inner surface to absorb fluid forces and a brazing layer for structural integrity, enabling accurate measurement of downhole fluid parameters under high pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a seal is used to prevent fluid leakage around the optical sensor body, then fluid sealing is improved, but the seal may fail under high downhole pressures up to 30 Kpsi
Solution Approach 1:
A backup ring is installed behind the seal to provide structural support and distribute high downhole pressures (up to 30 Kpsi) before they reach the seal. This pre-cushioning prevents seal failure by absorbing and dispersing the pressure load, ensuring reliable fluid sealing under extreme downhole conditions.
Solution Approach 2:
The optical window assembly combines multiple materials with complementary properties: a sapphire optical window for light transmission, an elastomeric seal for flexible sealing, and a rigid backup ring for structural support. This composite structure enables the assembly to withstand high pressures while maintaining both sealing integrity and optical functionality.
2Measurement precision
If an optical window is installed to allow light passage for fluid measurement, then optical measurement capability is enabled, but fluid may leak around the optical window assembly
Solution Approach 1:
The optical window assembly acts as an intermediary structure that simultaneously provides light transmission and fluid sealing. The assembly includes a sapphire optical window for light passage, surrounded by a sealed interface with backup ring support, creating a dual-function component that enables both optical measurement and reliable fluid containment under high pressure.
3Stress or pressure
If a traditional sealed structure is used to withstand high pressures, then pressure resistance is improved, but light transmission for optical sensing is blocked
Solution Approach 1:
The optical window assembly applies local quality by using a sapphire window material that is transparent to the specific wavelength of light used for fluid measurement. This localized optical property allows light transmission at the sensor interface while the surrounding backup ring structure provides pressure resistance, combining optical and mechanical functions in different zones of the same assembly.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration ensures reliable fluid analysis by preventing leakage and maintaining light intensity, allowing for precise measurement of downhole fluid parameters even at pressures up to 30 Kpsi, enhancing the accuracy and reliability of formation evaluation.
Implementation Method 1
an optical window positioned in the passage of the sensor body to pass the light from the flowline to the optical sensors
Implementation Method 2
The sensor body has a tapered inner surface
Data Source
AI summary
An optical window assembly of an optical sensor of a downhole tool positionable in a wellbore penetrating a subterranean formation. The downhole tool has a housing with a flowline there through to receive downhole fluid therein. The optical sensor is positionable about the flowline to measure light passing therethrough. The optical window assembly includes a tubular sensor body positionable in the housing (the sensor body having a sensor-end and a flanged signal-end with a passage there through), an optical window positionable in the passage of the sensor body to pass the light from the flowline to the optical sensors, a seal disposed about the sensor body, and a backup ring disposed about the sensor body between the flanged signal-end and the seal to support the seal about the sensor body whereby the downhole fluid is prevented from leaking between the seal and the sensor body.